engel



UNITE STATES PATENT Trice.

CHARLES R. ENGEL, or MONTPELLIER, nnuxumg FRANCE, AssIcronTo THEsooin'rr' or OARBONATE or reuse, or SAME PLACE.

MANUFACTURE OF CARBONATE OF POTASSIUM.

SPECIFICATION forming part of Letters Patent No. 252,653, dated January24, 1882.

Application filed November 21, 1881. (No specimens.) Patented in FranceDecember 30, 1880.

T all whom it may concern:

Be it known that I, CHARLES RoDoLPHE ENGEL, chemist, a citizen of theRepublic of France, and residing in l\lontpellfer, (Hraulh) France, haveinvented Improvements in the Manufacture of Carbonate 01' Potassium,(for which [have obtained a French patent, December 30, 1880, No.140,427,)of which the following is a specification.

to My invention consists in an entirely new method of manufacturingcarbonate of potash from any other soluble salt of potassium. It isbased upon the discovery that it either magnesia or a carbonate ofmagnesium be added 1 to an aqueous solution ot'a potassium salt, and

the resulting mixture be then heated by car bonic-acid gas, there isfound a double carbonate of magnesium and potassium,'l'rom whichcarbonate of potash may afterward be separated, as will hereinafter beset forth.

In describing how this invention is to be carried into effect I willsuppose that the potassium salt from which carbonate of potash is to'be, manufactured is potassium chloride. In such case an aqueoussolution of potassium chloride and carbonate of magnesium in afinely-divided state are charged .in to a suitable vessel furnished witha mechanical agitator, and the aperture by which these materials 0 wereadmitted is then closed by a suitable cook or otherwise. Theagitator isthen setin motion, and there is then sent into the said vesselcarbonic-acid gas, either at or above the atmospheric pressure.Absorption of carbonic 5 acid takes place with formation, on the onehand, of small crystals of a double carbonate of magnesium andpotassium, and on the other hand of chloride of magnesium. When carbonicacid ceases to be absorbed the reaction 4.0 is terminated. The contentsof the vessel in which the reaction has been performed are now drawnoftby a suitable cock into another vessel,in which theyarc allowed tosettle. The deposit consists of small crystals of the afore- 5 saiddouble carbonate of magnesium and potassium mixed or not with any excessof carbonate of magnesium which may have been used, while thesupernatant liquor is chiefly a solution of chloride of magnesium withany 5c excess of chloride of potassium which may have been employed. Thesupernatant liquor, however, contains also the elements of more doublecarbonate, which it is capable of depositing on longer standing. It istherefore drawn off into still another "esscl, in which it is allowed toremain until it has deposited as much further double carbonate as itwill. It is found to do this more rapidly if either magnesia oroxycarbonate of magnesium be added to it with agitation. Both depositsare then separated as Far as possible from the mother-liquor by meanscitherofa centrifugal hydroextractor or by a filter-press or othersuitable appliance, as will be well understood. The double carbonate ofpotassium and magnesium is thus obtained practically free. frommother-liqifor and from all foreign solids, except, perhaps, magnesia orcarbonate of magnesium, or both, and these are immaterial. It nowremains to separate carbonate ot' potash from the said doublecarbonate,aud this maybe done in either of two ways. If the doublecarbonate be boiled with water, it splits up into carbonic acid,carbonate of magnesium, and carbonate of potash. The carbonic acid goesoff as gas, and can be used for the production of more double carbonate.There remains a solution of carbonate of potash holding in suspensioncarbonate of magnesium. This solution can be readily separated from thesuspended carbonate of magnesium byfiltration, and from the filteredsolution commercial carbonate of potash can then be obtained either byevaporation to dryness, or by partial evaporation followed by coolingand crystallization, as will be well 85 understood. Or the doublecarbonate may be decomposed by heating it in the dry way, and theproduct be treated by water, and the resulting solution of carbonate ofpotash be then filtered from carbonate of magnesium, and thereafter bedealt with as already described. In either case the carbonate ofmagnesium filtered from the solution of'carbonate of potash should beused for the production of more double carbonate. It is to be observed,however, that 5 the quantity of carbonate of magnesium thus separatedbyfiltratiou from the solution of carbonate of potash will not be sogreat as the quantity which was originally added to the solution ofchloride of potassium commenced with, since a portion of the carbonateof magnesium commenced with has been converted into chloride ofmagnesium. If the motherliquor containing this chloride of magnesium beconcentrated by evaporation, and be then furtherevaporated to dryness,and the residue calcined in presence of vapor of water, the

chloride of magnesium will be decomposed into of magnesium mustbeemployed in eachsuccessive operation equivalent to the quantity ofcarbonate of potash obtained from the preceding operation; or, insteadof adding the carbonate 0t magnesium in the first operation, one may addfree magnesia, since what takes place in that operation when freemagnesia is present at the commencement of it is simply the conversionof that free magnesia into magnesium carbonate.

The double carbonate produced as above described will usuallyconsist ofone equivalen t-- or, say, eighty-t'our parts, by weight-ofnormalcarbonate of magnesium, (or MgCO combined with one equivalent-or, say,one hundred parts, by weightof bicarbonate of potassium, (or HKUO Q butit may also under some circumstances consist of one equivalent-or, say,eighty-tour parts, by weighte-ot'normalcarbonate of magnesium, (or MgO0combined with oneeqnivalent-or, say,onchundred and thirtyeight parts,byweight-0t monocarbonate of potassium,(orK OO or its constitution may beintermediate between these two extremes. The maximum and most usualquantity of can bonate of magnesium, or of free magnesia, to be employedin thefirst operation above described or, say, twentyfour parts, byweigh t-ot' metallic magnesium per one equivalentor, say, thirty-nineparts, by weigh't -of metallic potassium contained in the doublecarbonate produced. In some cases less than this proportion wouldsuffice; but the employment of a larger quantity of carbonate ofmagnesium, or

of magnesia, than the quantity contained in the double carbonateproduced will not be attended by any serious disadvantage.

From this description of the manner in which the present invention maybeperformed when it is applied to the manufacture of carbonate of potashfrom chloride of potassium,the manner of performing it when it isapplied to the manufacture of carbonate of potash from other salts ofpotassium will be fully understood. All the operations are the samewhatever salt of potassium be commenced with, except as regards thetreatment of the mother-liquor, from the first operation. When, forexample, the salt commenced with is sulphate of potas sium, the motherliquor will contain sulphate of magnesinm,which cannot be utilized inthe same manner as chloride of magnesium, but can be utiliz d in otherways, as will be well understood by practical men.

It should be added that this invention can be applied to double salts ofpotassium and magnesium, such as carnalite.

\Vhat I claim as my invention, and desire to secure by Letters Patent ofthe United States,

1. The method of producing carbonate of potassium fromothersalt-ofpotassium by forming a double carbonate of potassium andmagnesium in the manner explained and separating the carbonate ofpotassium from said double carbonate by boiling or by heating in a drystate, substantially as described.

2. The method ot'obtaining a double carbonate of magnesium and potassiumby treating by carbonic-acid gas a mixture of carbonate of magnesium,orfree magnesia, with an aqueous solution of a salt of potassium,substantially as hereinbet'ore described.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses. is thus the quantity containingone eqnivalen t j CHARLES RUDOLPH ['1 ENGEL.

\Vitnesses:

EU. Ismnnnae, OASTELOIZ.

